Purification of hydrofluoric acid



Jan.. 28, 1947.

@seringue-line!- u 'tn'od's offtreetiae nubile; edd; to,

we onwetend fie 'hihbo'lm'gf seidig herih ire. well-known .to pleV thevarticle Commer-V a-1iafmwfq :which ,l Metallislcel" Engineering'.'fari' November," 1943;

pas@ 12e i again '(vpl. so. No.` i115l on pas? thlt "with, ntinued 'usethe theiugnj-.boiungeontannnants beine .removed as.

spent allrylation 'hydro-m lcid-,soluble organicl contamina,ntsVreineyedjby distillation." 'on page', 121', tueii uthbrreiersgtotiiespent acidjrerunj system in 'which thefaid is` distilied overhead'Hemels 1 'Ifo pounds 'ofanhydrous hydroiluoric acid containing0-1193 percent by weight of sulfur d iozdde. wasadded 0.4'1l pound of acidfsolubleoil obtained from used acid from a commercial hydroiluoric.. acidalkylation plant for alkylating isobutane with oleilnsprinclpallybutylenes; the oilfcontained.v 0.170 per:v cent by weight of sulfur.

The 'calculated sulfur dioxide content of the niixtiire was 0,181-- per.cent byfweight. Themixtuewasshalen for two hours at room temperatureandvthen wasallowed to stand for two days ,untili it 'could be.conveniently fractionally distilled. The mixturewas .distilled at about135 to 1409;?, and 3o p, s. y1 givingl 5 .91 pounds of hydroiiuoricacidjoverheal with a sulfur dioxide content'of on lyi0.022. pery cent byweight. Further distillationfupjto a'tmperature of 300 F., gave it'4kettle. product." also' Australian Patent. y

117,350(acceptedlugist 5,;1943) which shows Mes. hydrogen fluride.catalyst phase. containing organic` contaminating.' materials to abettm'" hydoerbgli'fraetion consisting essere rtw'ul. be 'seerijtnetthepresent invention .pro-

' vides. advantages over cnventienl.

4is",tomadjdtlie fresh make-"up hy.-

ntiiedintheiresii and, obseetionably' contain ates the alkylate. Withmy' invention the 'only hydrofiuoricf'acidadded to settler 2 .fis

not marseille-end i ieeereili-Sibsttleuv 1ersL than 0.0,',llwcightgpercent of sulfur dic'ixivcle. even..

jlr'iverition y accomplishes nnfiiifriendenntfine man* dit 165"comprises admlxing said hydroiluorlc acid with so.. vblein4hydioiluoxic.acidt digestingithe resulting 0.0poundvotl--hydroiiuoricacid overhead with a sulfur dioxide content of 0,155 per cent by weight.The resulting-I residue, whenl heated to 400' F. liberated 0.025 poundof a gas, containing 19.65 per cent by w'elghtoi' sulfur dioxide and3.78 per i cent byweight of hydrogen sulilde, showing that i.. thesulfur-containingl compounds' decompose at thi'stemperature,The.residual oil;` after being heatedlto 400 F.,' containedA 0.674 percent by weight oi'vsulf'ur, or about tourtimes its original content.

' Example 2 In a commercial alkylation unit for the alkylation ofisobutane with olefins, principally butylenes, fresh hydroijluoricacidto make up loro acid lost in any'mannei .whatever is added to thestream ofusedfacid being removed from the settler for, regeneration,substantially as indicated in the drawing. The resulting mixture passesto a digesting tank inv which it is retained untilthe sulfur-dioxide inthetiesh acid'has reacted with theaidfsoluble oil in the used acid. Thenthis mixture is. passed to the acid-rerun system, wherein substantiallypure hydrouoricacid is `'distilled from lthe oil at about 135? F. and 30p, s. i.

"aboutl300`F., to give a relatively small fraction oi Distillatlon andheating is then continued .to

hydroiluoric'aci'd having alow but appreciable 'content'fof sulfurdioxide; this fraction is recycled to the'I digesting `tank.`r Theresidue, containing moist of the original sulfur dioxideias`highboilingsulfurcontaining compounds, is remoyedasa by-product oi theprocess.

I' 6.141.192 1. Theprocessoi rretrieving,sulfur dioxide fromhydroiluoric acid containing thesame whichL atleast partiallyspenttuhydroiluoric acid ywhich has beenusied in.v alirylationof`parains with oleflns with hydroiluoiic acid, said spent hydrofluoricacidl containing@ heavy. olefinic oil solumixturie for a period .of timesufllcient to effect reaction betweensubstantially all oisaid sulfurdioxide and said :oleflnic oilto yform complex sulvfur-containingAcompounds, and separating hydrvoiluorlc acid substantially free fromsulfur dioxidefromA a residualmaterial containing substantially allotsaidsul furcontaining compounds,

2. vThe process of removing sulfur dioxide from Ihydrofiuoric acid`containing the same which comprises admixlng said hydrouoric acid withat least partially spent hydrouoric acid derived fromalkylationofparaiilns withy oleiins in the presenceof hydrouonic acid,said Aspent hydroproduct to said alkylation step as the catalysttherefor. .s

10. In an alkylation process comprising the steps of alkylating parafnswith oleflns with substantially anhydrous hydrofiuoric acid as thecatalyst, passing the alkylation effluent to a settling zone and thereseparating it into two; phases namely a hydrocarbon phase containing thealkylate and a catalyst phase, separately withdrawing said phases,recycling a portion of said withdrawn vcatalyst phase -to saidalkylation step, passing ther balance of said withdrawn catalyst phaseto a fractional Vdistillation zone and therein distilling overhead alow-boiling fraction of substantially pure hydrofluoric acid from abottoms fraction containing high-boiling impurities derived from saidcatalyst phase, and recycling said overhead fraction of hydroiluoricacid to said alkylation and separation ',system, the improvement whichcomprises` commingling therentire amount of fresh hydrofluoric acidcontaining substantially more than (105 weight percent of sulfur dioxideused asm'a'le-up for said alkylation step with said balance of saidWithdrawn catalyst phase at a point outside of said alkylation andseparation system, digestin'gthe resulting hydrofluoric acid mixture atatemperature of fromr 50 t0t250 F. for a period of time suillcient toeffect reaction of substantially all of said s'ulfur dioxide witholefinic acid-soluble oil formed Vduring said alkylation and containedin said balance of said withdrawn catalyst phase to form high-boilingcomplex sulfur-containing compounds, and employing the resultingdigested mixtureas the feed'to said fractional distillation zoneandthereby substantitally freeing"said"recycled acid fraction from sulfurdioxidet 11. In a process for effecting the conversion of an organiccompound ,in the presence of concentrated hydroiluoric acid as aconversion catalyst, the improvement for avoiding contamination ofproducts of said conversion by sulfur compounds resulting from sulfurdioxide present as an impurity in make-up hydrofiuoric Yacid catalyst,which comprises separating from eilluents of said conversion liquidhydrotluoric acid catalyst, recycling a portion of said liquidhydrofluoric acid catalyst to said conversion, passing a further portionof said hydroiluoric acid to afractional distillation means toremove-impurities therefrom, intimately commingling the entire amountofv fresh sulfur dioxide-containing hydrofluoric acid from an extraneoussource to be added to the system as make-up with'a Vmaterial selectedfrom the group consisting of heavy olefinic oil formed A ly all of saidsulfur dioxide contained in said' fresh hydrofluoric acid with saidmaterial to Aform organic sulfur compounds, passing the mixtureresulting from said treatment and containing said organic sulfurcompounds to the aforesaid fractional distillation means, removing as alow-boiling fraction from said fractional distillation meanssubstantially pure sulfur dioxide-free hy-v4 drofiuoric acid and passingsame Vto said conversion. Y I l 12. A process for alkylating alkylatablehydrocarbons with oleiins inthe presence of concentratedhydrofluoricacid and avoiding contamination of the alkylate'bysulfur'compounds resulting from sulfur dioxide present as an impurity in-make-up hydrofluoric acid catalyst, which comprises reacting analkylatable hydrocarbon and an olen under alkylation conditions in thepresence of essentially sulfur-free hydrouoric acid as alkylationcatalyst, separating from eflluents of 'said alkylation liquidhydrouoric acid catalyst, recycling a portion of said liquidhydrofluoric acid catalyst to said alkylation, passing a further portionof said hydrofiuoric acid to a fractional distillation means to removeimpurities therefrom, intimately commingling with the entire amount offresh sulfur dioxide-containing hydrofluoric acid from an extraneoussource to be added to the system as make-up with a material selectedfrom the group consisting of heavy olenic oil formed in the alkylationof paratlins with olens with hydrouoric acid, and spent hydroiluoricacid containing olenic contaminants and maintaining the resultingmixture under reaction conditions such as to effect combination ofsubstantially all of the sulfur dioxide contained in said freshhydrouoric acid with said material to form organic sulfur compounds,passing the mixture resulting from said treatment and containing saidorganic sulfur compounds to the aforesaid fractional distillation means,removing as a low-bolling fraction from said distillation meanssubstantially pure sulfur dioxide-free hydroiluoric acid and passingsame to said alkylation.

13. A process for alkylatng alkylatable hydrocarbons with olelns in thepresence of concentrated hydrolluoric acid and avoiding contamination ofthe alkylate by sulfur compounds resulting from sulfur dioxide presentas an impurity in make-up hydrouoric acid catalyst, lwhich comprisesreacting an alkylatable hydrocarbon and an olefin under alkylationconditions in the presence of essentially sulfur-free hydroiluoric acidas alkylation catalyst, separating from eiiluents of said alkylationliquid hydrofluoric acid catalyst, recycling a portion of said liquidhydrofiuoric acid catalyst to said alkylation, passing a further portionof said hydrofiuoric acid to a fractional distillation means to removeimpurities therefrom, intimately commingling the entire amount of freshsulfur dioxide-containing hydrofluoric acid from an extraneous source tobe added to the system as make-up with said further portion of saidhydrofluoric acid and maintaining the resulting mixture under reactionconditions such as to effect combination of substantially all of thesulfur dioxide contained in said fresh hyd'roiluoric acid with olefiniccontaminants contained in said further portion of said hydroiluoric acidto form organic sulfur compounds, passing -the mixture resulting fromsaid treatment and containing said organic sulfur compounds to theaforesaid fractional distillation means, removing as a low-boilingfraction from said distillation means substantially pure sulfurdioxide-free hydroiluoric acid and passing same to said alkylation.'

'14. A- process for alkylating lalkylatable hydrocarbons with olens inthe presence of concentrated hydroiluoric acid and avoidingcontamination of the alkylate by sulfurcompounds resulting from sulfurdioxide present as an impurity in make-up hydrouoric acid catalyst,which comprises reacting an alkylatable hydrocarbon and an olefin underalkylation conditions in the presence of essentially sulfur-freehydrofluoric acidv as alkylation catalyst, separatinglfrom effluents ofsaid alkylation liquid hydrouori'c acid catalyst, recycling a portion ofsaid liquid hydrofiuorlc acid catalyst to said alkylation, passing afurther `portion of said hydrofiuorie acid to a fractional ydistillation means to remove impurities therefrom, intimatelycommingling the entire amount of fresh sulfur dioxide-containinghydrofluoric acid from an extraneous source to be added to the system asmake-up with a. heavy oleflnic oil formed in the alkylation of paraiilnswith olens with hydrofluoric acid and maintaining theresulting mixtureunder reaction conditions such as to effect combination of substantiallyal1 of the 10 sulfur dioxide contained in said fresh liydrofiuoric vacid with said heavy olenic oil to form organic sulfur compounds,passing the mixture resulting `from said treatment and containing saidorganic sulfur compounds to the aforesaid fractional distillation means,`removingyas a low-boiling frac tion from" said distillation` meanssubstantially pure sulfur` dioxide-free hydrofiuoric acid and passingsamen* to seid alkylation.

\ 5"* RALPH C. COLE.

